The SL is smoother ride, that's for sure, however, it still gets pushed around if going fast enough. If you are keeping the Evo, step up to the Heritage or something similar. That's just my opinion. The SL is noticeably more damp than the EVO, but if you're going to have a quiver of two, go all the way and cover both ends. The Evo and Sl aren't a bad quiver. The heritage would make a much better one IMO.
Or... just go all the way and get a Raptor!!!
Probably the 159...